Standard audio connectors or plugs are available in three sizes according to the outside diameter of the plug: a 6.35 mm (¼″) plug, a 3.5 mm (⅛″) miniature plug and a 2.5 mm ( 3/32″) subminiature plug. The plugs include multiple conductive regions in distinct portions of the plug such as the tip, sleeve and one or more middle portions between the tip and sleeve and are thus often referred to as TRS (tip, ring and sleeve) connectors.
FIGS. 1A and 1B illustrate examples of audio plugs 10 and 20 having three and four conductive portions, respectfully. As shown in FIG. 1A, plug 10 includes a conductive tip 12, a conductive sleeve 14 and a conductive ring 16 electrically isolated from the tip 12 and the sleeve 14 by insulating rings 17 and 18. Plug 20, shown in FIG. 1B, includes a conductive tip 22, a conductive sleeve 24 and two conductive rings 25, 26 electrically isolated by insulating rings 27, 28 and 29. When plugs 10 and 20 are 3.5 mm miniature connectors, the outer diameter of sleeve 14, 24 and conductive rings 16, 25, 26 is 3.5 mm.
A standard receptacle or “jack” used to connect an audio plug, such as plug 10 or 20, to an electronic device includes an opening through which the plug is inserted that has an interior diameter sized to receive the plug. Taking into account the thickness of the housing in which the opening is formed as well as an appropriate amount of clearance for the plug to slide into the receptacle, a standard receptacle for a 3.5 mm audio plug has a thickness that is greater than 3.5 mm. As electronic devices get thinner, the diameter of the audio plug, and corresponding receptacle, have been found to be limiting factors in reduction of device thickness. While it is possible to develop plugs that are thinner than either the 3.5 mm miniature or 2.5 mm subminiature audio plugs that could be used with a correspondingly thinner receptacle, smaller connectors are not backward compatible and need to use an adapter for larger jacks.